TRAJECTORY-DEPENDENT CHARGE-EXCHANGE IN ALKALI ION-SCATTERING FROM A CLEAN METAL-SURFACE

We report the first evidence for trajectory-dependent neutralization o f hyperthermal energy alkali ions scattered from a clean metal surface . We have scattered 7.5 and 50 eV Na+ from Cu(001) and found that, for atoms leaving the surface with the same velocity and direction, the m easured neutral fraction varies by a factor of 7 depending on the type of surface collision. The collision types are identified with scatter ing simulations. We suggest that coupling of the charge exchange and c ollision dynamics is responsible for the variations in neutralization.